package com.JavaWeb.dao;

import com.mysql.cj.protocol.Resultset;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块，类加载的时候就初始化
    static {
        Properties properties = new Properties();
        //通过类加载器读取对应的资源
        InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");

        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver=properties.getProperty("driver");
        url=properties.getProperty("url");
        username=properties.getProperty("username");
        password=properties.getProperty("password");
    }

    //获取数据库连接
    public static Connection getConnection() throws Exception {
        Class.forName(driver);
        Connection connection = DriverManager.getConnection(url, username, password);
        return connection;
    }

    //编写查询类
    public static Resultset execute(Connection  connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException {
      //预编译的SQL，在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);
       for (int i=0;i<params.length;i++){
           //setObject占位符从1开始，但是我们的数组是从0开始
           preparedStatement.setObject(i+1,params[i]);
       }
     resultSet = preparedStatement.executeQuery();
       return (Resultset) resultSet;

    }
    //编写增删改方法
    public static int execute(Connection  connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        //预编译的SQL，在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);
        for (int i=0;i<params.length;i++){
            //setObject占位符从1开始，但是我们的数组是从0开始
            preparedStatement.setObject(i+1,params[i]);
        }
        int updateRows = preparedStatement.executeUpdate();
        return updateRows;
    }
    //释放资源
    public static boolean closeResource(Connection  connection,PreparedStatement preparedStatement,ResultSet resultSet){
        boolean flag=true;

        if (resultSet!=null){
            try {
                resultSet.close();
                //GC回收
                resultSet=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        if (connection!=null){
            try {
                connection.close();
                connection=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        if (preparedStatement!=null){
            try {
                preparedStatement.close();
                preparedStatement=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        return flag;
    }
}
